The sol-gel process for forming glass is well known in the art. Further, it is well known to fabricate passive devices such as waveguides, splitters and directional couplers, and grating structures as well as thermo-optic switches using photolithographic processes. Canadian Demand Application No. 2,218,273 describes a solvent-assisted lithographic process in use by Lumenon Innovative Lightwave Technologies, Inc. and is incorporated herein by reference.
The above-identified patent describes a process including the sequence of steps for forming a silicon dioxide layer on a silicon substrate, depositing a photosensitive sol-gel layer on the silicon dioxide layer, exposing the sol-gel layer to a pattern of ultra violet light to solidify portions of the sol-gel layer, and (wet) etching to remove the non-solidified portions of the sol-gel layer. The solidified portion of the sol-gel layer, in one embodiment, comprises an elongated ridge for defining a waveguide. A cladding layer is added on top of the ridge resulting in a non-planar surface.
A doctoral thesis entitled: “Photolithography of Integrated Optic Devices in Porous Glasses”, City University of New York, 1992 by E. Mendoza, one of the applicants herein, describes techniques for fabricating integrated optic devices in porous glass employing a variety of reactants. The thesis describes sol-gel as a technique for forming bulk porous glass.